Multispeed motor control system



1930. E. D. HARRINGTON 1,743,772

Inventor:

.EI i ioct D. Harri n/cigton,

H is Air'cohn ey.

7 sequence and at proper'time intervals.

Patented Jan. 14, 1930 UNITED STATES PATENT OFFICE ELLIOTT D. HARRINGTON, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK MULTISPEED MOTOR CONTROL SYSTEM Application filed July 2, 1928. Serial No. 120,204.

7 My invention relates to the control'of electric motors, particularly multi-speed electric motors, employed in elevator or other similar service where the motors are frequently ac- 8 celerated and retarded, and also are operated as braking generators under certain conditions.

The invention provides improved controlling apparatus whereby upon operation 10 of a simple form of master switch the several controlling operations necessary to start the multi-speed motor and efiect a smooth and satisfactory acceleration to any selected speed are performed automatically in the prpfier so my improved controlling apparatus automatically functions to control the retardation of the motor and to establish braking connections for the motor for a limited time.

fill interval under suitable operating conditions.

Briefiyyin accordance with my invention all of the various controlling operations are accomplished in the proper sequence and at the proper time interval by means of a single se uencing and timing relay, which is simple an inexpensive in construction, positive and reliable in operation, and moreover, is readily adjustable to meet controlling requirements varying widely in number, sequence, or

timing.

While my present invention may be readily adapted to control both alternating current and direct current motors employed in service of the above character, it is particularly advantageous when embodied in a twospeed alternating current elevator control equipment. The single figure of the accompanying drawing is a schematic diagrampr" a preferred form of the invention embodied M in such apparatus.

in the drawing the multi-speed elevator driving motor 10 which is to be controlled in accordance with my invention is shown as a well known form of alternating current induction motor having the squirrel cage rotor 11 suitably connected to the elevator driving mechanism (not shown) and the stator windlugs 12 arranged to be interconnected to form different numbers of poles as for example,

eight poles and four poles, for operation of the motor 11 at low speed and at high speed respectively. It will be understood. that as far as my present invention is concerned, the manner of connecting the motor to the elevator driving mechanism and also the manner of arranging the motor windings to obtain multi-speed operation are immaterial and may be accomplished in any desired way. In accordance with the usual practice, an electromagnetic friction brake (not shown) having a movable braking member biased into engagement with a suitable rotating part of the motor or of the elevator driving mechanism preferably is employed to stop and securely hold the motor at rest.

For low speed operation power is supplied to the stator windings of motor 10 from the three phase power supply lines 15 through the line switch 16 and either one of the reversing switches 17 and 18 with the speedchanging switch 19 in its biased osition in which it is shown. For high spee operation or the motor the speed-changing switch 19 is operated to its upper position.

"Each of these switches is of the electromagnetically operated contactor type and is biased to the open position in which it is shown. The acceleration of the motor 10 to the low operating speed is controlled by the electromagnetic contactor 20, while the acceleration to the high operating speed is controlled by the electromagnetic contactor 21. Accelerating contactor 20 controls a short circuit around the resistor R which is permanently connected in the low speed circuit ofthe motor and accelerating contactor 21 controls the short circuit around the re sistor R which is permanently connected in. thehigh speed circuit of the motor.

To efiect electric braking operation of the motor the speed changing switch 19 is operated to establish the low speed power connections when the motor 10 is operating at a higher speed to permit the motor 10 to return power to the supply line 15 through the reversing and line switches until the speed of the rotor 11 is reduced to the low speed value.

In accordance with my present invention the several electromagnetic contactors pre- The relay 23 is preferably, although not necessarily, of the induction disk type described and claimed in U. S. Patent No. 1,620,555 to Jones and Wilfe, and dated March 8, 1927, and has the operating windings A and A? arranged to produce a single phase torque for rotating the disk D in a counter-clockwise direction. v The operating windings B and B when suitably energized, serve, in conjunction with the windings A and A, to produce a polyphase torque for rotating the disk D in a clockwise direction. The disk D is mechanically connected as by means of the rack and pinion gearing 24 to reciprocate the actuating plun er or cam 25 between the position in which it is shown and the position in which it engages with the stop 26. The several circuit controlling contacts C of the relay 23 are suitably spaced alon the supports 27 and 28 and are provided wit h actuating pins extending' into the path of the actuating cam 25 to be actuated thereby. The contacts C are separately ad'ustable upon the supporting bars so that t e sequence in which the contacts are operated and also the time interval between the operation of the successive contacts may be varied at will. The arrangement also readily permits the number of thecontacts to be varied to meet widely varying motor starting and speed regulating controlling requirements. When the contacts C are once roperly adjusted and secured to the bars 2 and 28 thesequence in which the contacts are operated upon movement of the actuating cam 25 in each direction is. defi-' nitely fixed. Likewise, as the disk D is alive s operated at a substantially constant spee in each direction. the time interval between actuation of the successive contacts upon the resulting travel of the. actuating cam 25 is definitely fixed meagre ing circuit for the up. reversing switch 17 is established extending from the lower su ply conductor 15 through the two upper rig t hand contacts of the master switch 22 bridged by the movable contact 22 the normally closed relay contact G, the interlocking contact 29 of the line switch, thence through the operating winding of reversing contactor 17- to the middle supply line 15. As the reverse contactor 17 closes, a holding circuit in parallel to the relay contact 0" is completed through the contact 30 and at the same time the operating winding of line switch 16 is ener ized through the contact 31. spee -changing switch 19 normally is in its low speed position as shown, the closure of the line switch 16 completes the low speed power connections for the motor 10 with the resistors R, R in the low speed energizing circuit. The rotor 11 of the motor 10 at once starts to rotate in the up direction as determined by the reversing switch 17, and the resistors R, R are properly proportioned to limit the motor starting torque to a value suitable for eiiecting smooth starting of the elevator. I

The automatic sequencing and timing relay 23 now comes into action to automatically control further operation of the motor 10. As soon as the line switch 16 is closed the windings B and B qt the relay 23 are energized through a circuitextendin through the upper contact of line switch 16, t e conductor 34, the normall closed relay contact (3,, of the operating win ings B and B the conductor 35, through the middle contact of line switch 16 to the middle supply line 15. The pol phase torque exerted on the disk D by the joint action of operating windings A and A and B and B set the disk into rotation in a clockwise direction. This results in the operation of the actuating cam 25 to the right at a substantially constant s eed.

In its travel to the right the operating cam 25 first engages with and operates the normally closed contacts C" and 18 to their respective openpositions. After a time intervalsuificient to permit the motor 10 to fully accelerate with the resistors R and R inthe energizing circuit'the cam 25 engages with and operates the normally open contact (3 to the closed position to establish an energizing circuit for the low speed accelerating contactor 20. This circuit may. be traced from the middle supply line 15 through the operating winding of contactor 20, the normally closed relay contact 6', the. relay contact Q thence through the conductor 32, to the lower supply line 15. The accelerating contactor 20 closes the short circuit about the nesistorsR to increase the torque of motor 10 and permit the motor to accelerate the elevator to full low speed with the stabilizing resistors-R in circuit with the motor windings 1.2.

Since the As the operatin' cam 25 continues its travel to the right, t e normally open contact supply lines 15 and the conductor 36, closure of relay contact C completes the energizing circuit for the operating winding of the speedchanging switch 19, and the latter at once operates to interrupt the low speed power connections of the motor 10 and establish the high speed connections of the resistors R and R in circuit with the motor winding 12. However, if the master switch 22 remains in position a, the energizing circuit for speedchanging switch 19 is not established and the operating cam 25 continues its travel until the normally closed contact C is engaged and operated to the open position. The opening of contact C interrupts the circuit through which the relay operating windings B and B are energized and, consequently, the single phase torque of the operating windings A and A starts the disk D rotating in the reverse or counter-clockwise direction. As soon as the operating cam 25 is moved to the left sufiiciently to permit contact C to reclose the energizing circuit for the rela operating windings B and B, the disk D resumes its clockwise rotation and the camv25 again is operated to the right to reopen the contact C The periodic oscillation of the actuating cam 25 continues while the master switch 22 is maintained in the position a.

To accelerate the motor 10 to full high speed, the master switch 22 is advanced into the high speed position b. This serves to establish the energizing circuit for the oper-- ating winding of speed-changing switch 19 as previously pointed out and switch 19 immediately operates to open the low speed Dower connections of the motor and close the high speed connections for motor 10, the two lower contacts of speed-change switch 19 serving to interconnect the mid-points of the motor windings 12 in a well known manner so as to decrease the number of poles produced by the windings. The resistors R and R serve to limit the motor torque sufficiently to produce a smooth transition into the high speed connections.

With the speed-change switch 19 closed, the relay contact C is shunted by the auxiliary contact 37 with which the speed-changing switch 19 is provided. This permits continued energization of the relay windings B and B after the relay contact C is opened. Hence the operation of the actuating cam 25 to theright is continued and the relay contacts C'" and (1' are next engaged and operated to the closed position. function in conjunction with the loweriaux- These contacts.

iliary contact 38 of the speed-change switch to establish a maintaining circuit for the motor line and reversing switches to produce braking operation in a manner which will be described presently.

As the operating cam 25 continues its travel to the right the contact C- is opened to deenergize the low speed accelerating contactor 20 and the contact C is subsequently closed after the proper time interval to complete an energizing circuit for the high speed accelerating contactor 21. Upon the resulting short circuiting of the resistors It the motor 10 accelerates to full running speed with the regulating resistors R in the high speed motor connections. Movement of actuating cam 25 to the right continues until the cam engages with the stop 26 whereupon the induction disk D is stalled.

When it is desired to stop the motor 10 the master switch 22 may be thrown directly to the off position. This interrupts the energizing circuit for speed-changing switch 19 and the latter operates in accordance with its bias to reestablish the low speed power connections for the motor with both the resistors R and R in the low speed circuit. A maintaining circuit for holding the line switch 16 and the reversing switch 17 is established through the contacts 38 and 0'" upon the re- 5 turn of the speed-changing switch 19 tothe low speed position. Thus even though the master switch 22 is returned to the oil position, the motor 10 is maintained connected to the supply lines 15 under the complete control of the relay 23. The maintaining circuit for the reversing switch 17 may be traced from the motor supply line through the conductor 82, the contact 38 with the speedchange switch 19 in the low speed position, the contact 0' thence through the auxiliary contact 30 and operating winding of reversing contactor 17 to the middle supply line 15. Operating winding of line switch 16 is maintained energized through the auxiliary contact '31 of the reversing contactor 17. It will be evident that in case the speed-change switch 19 should fail for any reason to return to the low speed posit-ion, contact 38 will remain open and the line switch 16 and reversing switch 17 will be deenergized immediately upon operation of the matter controller 22 to the off position and thus at once disconnect the motor 10 from the supply lines 15.

As long as the actual operating speed o1 the motor 10 is above the normal low speed value the motor functions as a regenerative brake to slow down the load driven by the motor and return energy to the supply lines 15. Both of the resistors R and R serve as buiier resistors to limit the braking torque exerted by motor 10 to a. value just sufficient tially established with the motor operating at full high speed.

Simultaneously with the establishment of the braking connections of motor 10 by the return of speed-changing switch 19 to its-bias position, the energizing circuit of the operating windings B and B of relay 23 is interrupted at the contact 37. As a result, the single phase torque of operating windings A and A immediately start the return movement of the actuating cam 25 to the left. After the cam 25 leaves the stop 26 the contact C is permitted to open and deenergize the high speed accelerating contactor 21. Continued movement of the actuating cam to the left next permits the contact CF to close the energizing circuit for the accelerating con- I tactor 20. "When the contactor 20 closes the nections for the motors an resistors R are removed from the braking circuit of the motor 10 to allow an increased braking torque to be obtained so as to increase the retarding eli'ect upon the elevator. Further return movement of cam 25 serves to open the contacts C' and C' after a time interval during which the increased braking torque of the motor 10- ordinarily is capable of reducing the speed of the motor to substantially the normal low speed value.

Upon the opening of contact 6'" the maintaining circuit for the reversing switch 17 and the line switch 16 is interrupted and these switches open in accordance with their bias and disconnect the motor 10 from the supply lines 15. lhe return movement of actuatin cam 25 .to the left continues until the initia position is reached in which the disk D is stalled. I

lit should be noted that until the cam 25 is returned to the initial position, it is impossible to reconnect the motor 10 to the supply lines 15 due to the fact that the energizing circuit for the reversing switches 17 and 18 are interrupted respectively by the relay contacts C" and G. This efiectively prevents operation of the several motor controlling switches in an improper sequence at an improper time. p I

In case the master switch 22 is operated to the left into either the low speed vposition a or the high speed, I), exactly the same sequence of operations in accelerating motor 10 is produced by the relay 23 exce t that the reversing switch 18 instead 0 switch .17 is closed. Likewise, the switching sequence in establishin the braking conin disconnecting the motor from the su ply lines 15 is the same as that previously escribed.

From the foregoin it will be seen that a control equipment em odying my present invention is entirely automatic in its operation and absolutely insures the proper sequence and timin of the switching o erations to give smoot acceleration and the eceleration, as well as braking operation 033 the motor.

reversing v meagre Furthermore, all the sequencing and timing operations are combined in a sin le relay which is ositive in its action and readily permits a justment tomeet almost any desired motor controlling conditions. The unitary sequencing and timing relay also has the additional advantage that the exact seguence and the relative timing is visually in icated by the location of the several relay contacts alon the path of travel of the actuating cam, t us greatly facilitatin proper timing adjustment of the sequencing an operations.

It will be understood that although I have illustrated and described a preferred embodiment of my invention, the arrangement shown is susceptible of considerable modification to meet various operating requirements without departing from the true spirit and scope .of the invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a system of motor control, a motor, switch mechanism for controlling the starting and speed regulation of said motor,-an electro-responsive device provided with a plurality of windings, operable in different directions for controlling said switch mechanism, a master switch and connections controlled thereby through which said masterv switch controls all of said windings to operate said electro-responsive device in one direction to vary the speed of the motor, and controls only a portion of said windings to vary the speed of the motor in the opposite sense.

2. In a system of motor control, a motor,

switch mechanism for controlling the accelerating and decelerating operations of said motor, an electro-responsive rela havin a plurality of windings and a move. le mem r set one of said mainder of said windingsls energized to co operate with said portion to operate said ele ment in the opposite direction to efiect the other of said operations.

3. In a system of motor control, a motor,

switch mechanism including a series of separately movable contacts for controlling the starting and accelerating operation andthe decelerating and stopping operation of said. motor, a master switch and an electro-respon-- vmined time intervals, and connections con trolled by said masterswitch through which all of said windings areenergized to operate said series of contacts in one direction to.

, biased to a predetermined position and operable to a second position to control the starting and stopping operations of said motor, an ele0tro-responsive device for operating said series of contacts in a predetermined sequence after predetermined time intervals, said device being provided with a plurality of windings, a master switch and connections controlled thereby through which all of said windings are energized to operate said contacts from their biased positions to effect one of said operations.

-5. In a systemof motor control, a motor, electroresponsive switch mechanism operative to effect starting of said motor, separately operable switches operative to effect speed regulation of said motor, an electroresponsive device having a plurality of windings for controlling the operation of said switches, a portion of the 'windings of said electroresponsive device being connected to be normally continuously energized to eflect operation of said switches to decelerate the motor, a master switch, and connections controlled thereby through which said motor starting switch mechanism is operated and the remainder of the windings of said electroresponsivedevice are energized to effect operation of said switches to accelerate the motor.

6. The combination with an electric motor having low speed and high speed connections, of means including a master switch and a time element electroresponsive relay controlled thereby and having a series of contacts corresponding respectively to said low speed and said high speed connections arranged to be operated sequentially after predetermined time intervals for successively establishing the low speed and high speed power connections of the motor and controlling the acceleration of the motor to each operating speed.

7. The combination with an electric motor having low speed and high speed connections, of means including a master switch having a low speed and ahigh speed position and a cooperating electroresponsive relay having a series of contacts corresponding respectively to said low speed and said high speed connections arranged to be operated successively at predetermined time intervals after operation of the master switch to either the low or high speed positions for controlling the starting and acceleration of the motor to the corresponding operating speed.

8. The combination with an electric motor having low speed and high speed connections and a plurality of separately operable electroresponsive switches for establishing the low speed and the high speed power connections for the motor and controlling the acceleration of the motor to each speed, of an electroresponsive relay having a series of contacts corresponding respectively to said low speed and said high speed connections arranged to be operated in sequence at predetermined time intervals for automatically controlling the energization of said electroresponsive switches to prevent establishment of the high speed motor connections for a predetermined time interval after the establishment of the low speed motor connections and for automatically controlling the acceleration of the motor to each operating speed.

9. The combination with an electric motor having low speed and high speed connections and a plurality of separately operable electroresponsive switches for establishing low speed and high speed connections for the m0- tor and controlling the acceleration of the motor to each speed, of means including a master switch and a time element electroresponsive relay controlled thereby and having a series of contacts corresponding respectively to said low speed and said high speed connections arranged to be operated in sequence at predetermined time intervals for controlling the energizing circuits of said separately operable electroresponsive switches to successively establish the low speed motor connections, accelerate the motor to full low speed, interrupt the low speed connections, establish the high speed connections and accelerate the motor to full high speed at predetermined time intervals after operation of the master switch.

10. The combination with an electric motor having low speed and high speed connections,

of means including a master switch and a' time element. electroresponsive relay controlled thereby and having a series of contacts corresponding respectively to said low speed and said high speed connections arranged to be operated sequentially after predetermined time intervals for successively establishing the low speed and high speed power connections of the motor and controlling the acceleration of the motor to each operating speed, said relay having contacts for automatically establishing braking power connections for the motor after operation at high speed.

11. The combination with an electric motor having low speed and high speed connections, a separately operable line switch mechanism, electroresponsive speed changing switch mechanism, and electroresponsive accelerating switch mechanism for the motor, of means for controlling said switch mechanisms including a time element electroresponsive relay having a series of contacts arranged to be 0 erated successively at predetermined time intervals, and connections controlled by asserts said relay for operating the said separately operable electroresponsive switch mechanisms to successively establish the low speed and hi h speed power connections of the motor an control the acceleration of the motor to each operating speed, said relay havingthe said series of contacts arranged so that the low speed power connections for the motor are automatically established for a predeterm mined time interval after operation thereof at high speed.

.12. The combination with an electric motor having low speed and hie'h speed connections, a separately operable e ectroresponsive line s switch mechanism and electrores onsive speed-changing swltch mechanism or themotor, of means for controlling said switch mechanisms including an electroresponsive relay having a series of contacts. arranged to be operated successively after a predetermined time interval for insuring establishment of the low speed power connections of the motor for a predetermined time interval before and after establishment of the high speed ower connections of the motor.

13. he combination with an alternating current electric motor having low speed and high speed connections, a separately operable electroresp'onsive line switch mechanism,

electroresponsive speed-chan 'ing switch mechanism, and electroresponsrve accelerating switch mechanism for the motor, of means for controlling said switch mechanisms including an electroresponsive relay having a series of contacts arranged to be 0 erated successively after a gedetermined tlme interval for insuring esta lishment of the low speed ,gower connections ofthe motor for 'a pres v etermined time interval before and after 40 establishment of the high speed power connections of the motor.

In witness whereof, Ihave hereunto set my hand this 30th 'da 1 of June, 1926.

1 10 RINGTON, 

